1. Technical Field
The present invention relates to a lighting device, and more particularly, to a lighting device with color temperature adjusting functionality.
2. Description of Related Art
Recently, with the development of optoelectronics industry, more and more types of illumination device are proposed, in which the industry relating to the illumination device using LED chips as light-emitting devices thereof is regarded as star industry. According to manufacturing process, LED chips can be divided into high CT (color temperature) LED chips and low CT (color temperature) LED chips. If the illumination device uses the high CT LED chips as the light-emitting devices thereof, the light outputted by the illumination device called “cold light” (around 7000K); On the contrary, If the illumination device uses the low CT LED chips as the light-emitting devices thereof, the light outputted by the illumination device called “warm light” (around 3000K). So that, it is able to know that, whatever cold light or warm light, it is apparently divergent from the natural sunlight, and such divergence results in distinguishing sensibility for human eyes.
Accordingly, illumination device manufacturer make great efforts to fabricate and then propose a CT (color temperature) adjustable white light illumination device. A user is able to adjust the color temperature of the light outputted by the light illumination device. Please refer to FIG. 1, which illustrates a framework diagram of a conventional CT adjustable white light illumination device. As shown in FIG. 1, the CT adjustable white light illumination device 1′ includes: an array, which is formed by crosswise arranging a plurality of first LED chips 2′ and a plurality of second LED chips 3′. In the framework of the CT adjustable white light illumination device 1′, the first LED chip 2′ is able to emit a WW (warm white) light with the color temperature thereof ranging in 2500K-4000K, the second LED chip 3′ is able to emit a CW (cold white) light with the color temperature thereof ranging in 6000K-10000K. Moreover, as shown in FIG. 1, the WW light 4′ and CW light 5′ are combined to an output light 6′, wherein the color temperature of the output light 6′ depends on the relative contribution proportion of the WW light 4′ and CW light 5′.
So that, by way of crosswise arranging the plurality of first LED chips 2′ and the plurality of second LED chips 3′, the framework of the CT adjustable white light illumination device 1′ is completed; Moreover, the user can use a controlling module (not shown in FIG. 1) to adjust the relative contribution proportion of the first LED chips 2′ and the second LED chips 3′, so as to make the CT adjustable white light illumination device 1′ emit the output light 6′ with a selected color temperature. Please refer to FIG. 2, which illustrates a framework diagram of a controlling module of the conventional CT adjustable white light illumination device. As shown in FIG. 2, the controlling module 20′ used for controlling the first LED chips 2′ and the second LED chips 3′ includes a variable resistor Rw and a current source I, wherein the value of a first driving current IA and a second driving current IB can be adjusted by way of modulating the variable resistor Rw, such that the relative contribution proportions of the first LED chips 2′ and the second LED chips 3′ are adjusted.
Thus, through above descriptions, it is easily to know that the conventional CT adjustable white light illumination device 1′ provides the function of color temperature adjustment to the user, and the user is able to adjust the color temperature of the light outputted by the CT adjustable white light illumination device 1′ according to his preferences, so as to obtain a with light capable of comforting human eyes. However, the conventional CT adjustable white light illumination device 1′ still has shortcomings and disadvantages as follows:                1. As shown in FIG. 1, the first LED chips 2′ and the second LED chips 3′ are arranged to an array and driven by the same current source I; thus, if the current source I is unable to work, all the first LED chips 2′ and the second LED chips 3′ are unable to emit light.        2. As shown in FIG. 2, in the framework of the conventional CT adjustable white light illumination device 1′, the value of the first driving current IA and the second driving current IB are adjusted by way of modulating the variable resistor Rw, so as to adjust the relative contribution proportions of the first LED chips 2′ and the second LED chips 3′; thus, it can know that, if the variable resistor Rw is unable to work, it can not adjust the relative contribution proportions of the first LED chips 2′ and the second LED chips 3′.        
Accordingly, in view of the conventional illumination device and the conventional CT adjustable white light illumination device still have shortcomings and drawbacks, the inventor of the present application has made great efforts to make inventive research thereon and eventually provided a lighting device with color temperature adjusting functionality.